This book is an enjoyable read. With its serious title, a potential reader might expect this book to be hard work, but it isn't. It may help to have some knowledge of therapy as a practice, and an interest in research, but the language is easy to understand and complex ideas are explained clearly - I managed to read most of the volume during a longish train journey and was as engaged with its contents as I might have been with some novels. The authors have done a thorough job of presenting research findings from studies that aim to find out if and how therapy works, and what makes a difference to the outcome; they also discuss the implications for therapy practitioners. This summary may not make the book sound too much like fun, but the style and approach are accessible, down to earth and even humourous. Knowing the authors, and having received the copy from them, I was pleased to find that I can and do recommend it strongly to those who want to know about this topic.